Handheld electronic devices such as cellular telephone and tablet computers are often used within moving vehicles. Depending upon whether the user of the device is a driver or passenger, using the device for some services such as reading or writing text messages may be dangerous and/or illegal. Some existing devices such as geolocation receivers will disable text entry (e.g., entry of destinations) while a vehicle is in motion, even though a passenger may be the person attempting entry. Adding such a generalized prohibition on text entry to personal handheld electronic devices would undermine their usefulness, making such a solution impractical.